66 Nova wheel and tire sizes

[Sinco]

Getting ready to select and need some input. I can fit an 8x18 in the front and am undecided whether to put 18s in back or step up to 19s and would 20s be out of the question? I can fit up to 11" wide because I'm tubbing the car. I'm also looking for the proper tire fitment regardless if I go 18s, 19s, or 20s in the rear. I've been told the car will have a more aggressive stance if I run a taller wheel in the back. The problem going with 19s or 20s is there are limited tires available. I also want to be careful not to get the rubber band look by going with to short of tire. BTW I'm going with a 7 spoke wheel by DPE.